JPS5856755A - Method of monitoring clamping force of clamping device for machine tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for monitoring the tightening rate of machine tool tightening equipment by sequentially measuring the tightening rate and comparing the measured values with predetermined limit values. .

In order to increase the utilization rate of machine tools, and in particular to automate the manufacturing process on a large scale as much as possible even without the constant presence of workers, in addition to the control equipment that performs automatic production, we also introduce automatic loading into machine tools. Automatic installation and i-small equipment, machines,
Process monitoring devices are also known which allow the manufacturing process to be carried out in a prescribed manner taking into account the reliability of tools and workpieces.

When monitoring the machining process of machine tools, especially when cutting metal with a lathe, up until now the holding force of the tightening device during the machining process has not been monitored. Tightening is a weak point of machine tools that becomes important especially in high cutting capacity. Such a large tightening can only be achieved by a well-lubricated device. Therefore, for the reliability of the processing process, the operating status of the tightening device must be constantly monitored.

This is because physical, frictional and chemical effects can cause the tightening force of the device to decrease rapidly. These problems were actually considerably underestimated, since the reduction in force during the machining process was not known until now. These issues were also not very important. However, with the development of numerically controlled machine tools and the use of modern cutting materials of higher capacity, the tightening of machine tools has become more difficult. sex has increased significantly, but this has not been well known until now.

There is a force measuring device for tightening equipment for machine tools. It is up to the operator whether or not to perform this measurement. Due to the construction of the known measuring device, measurements can only be taken irregularly, since tightening generally requires repositioning of the pawls in order to take a measurement. Comparing the respective measured value (actual value) with a predetermined limit value (target value) and preventing the holding force required for a reliable machining process from falling below this target value is therefore not carried out regularly; Nor is it necessarily done. Since the use of known measuring instruments and the timing of the actual value-setpoint value comparison are left to the operator of the machine tool, it is not guaranteed that the machining process will only be carried out under the specified conditions. The danger of the necessary tightening being below the force plate cannot be eliminated.The problem addressed by the present invention is that when tightening a machine tool, the holding force of the device must be forcibly monitored, and the necessary It is an object of the present invention to provide a method that allows the machining process to be carried out only when a sufficient holding force is ensured.

Clamping is used to transmit force. All known clamping devices are used to transmit force. Because the sliding condition of the transmission surfaces is aggravated during the lubrication process due to the high loads of the transmission device, the holding force of the device is The solution to this problem according to the invention is that the tightening force decreases with the number of measuring cycles, so that the tightening force decreases with the number of measuring cycles. During the tightening process, the instantaneous tightening of the tightening device is measured, and from the measured value, the tendency of the force change in terms of the number of tightening processes is found, and after the last measurement process, the limit value is determined. Before what is expected to happen: Processing process? It is characterized by generating an interrupt signal.

By means of this method according to the invention, the tightening of the device is continuously monitored after a predetermined measurement period, so that the tightening remains at a limit value for the reliability of the knife, regardless of the operator. Be able to do that.

This automatically monitors the holding force of the workpiece during machining, eliminating routine and tedious processes and eliminating the need for the operator to decide whether to perform force measurements during tightening. The weaknesses that existed in the series of monitoring up to now will be improved, and the reliability of the tightening process will be significantly improved.

Finally, the force monitoring integrated into the processing process and the maintenance guaranteed by the method of the invention of the limit values for the clamping forces reduce the hitherto usual safety factors for the clamping process. As a result, it is possible to improve the quality of the product and obtain higher cutting capacity with less energy consumption.

The signal that is generated in time to interrupt the machining process before the tightening force falls below the limit value by the method of the present invention can be an acoustic signal or an optical signal, and this signal allows the operator to Interrupting the machining process, the clamp takes the necessary measures to increase the force, in particular the clamp lubricates the equipment. In a development of the method according to the invention, signals are used to prevent restarting of the machining process by stopping the machine tool.

As a result, the method of the present invention is integrated into the control of the machine tool, so that the required tightening force can be automatically prevented from falling below a predetermined value via the machine tool control device.

The method according to the invention ensures that the tightening remains optimal for the device during the process by means of monitoring logic controlled by a microprocessor. Predetermined data, such as tightening force, for example, are compared with actual measured values, predictions are made about the reliability of the tightening, and diagnostics inform the operator about the measures to be taken.

The method according to the invention takes into account the conditions actually present in the device during the machining of the workpiece, the device implementing the method stores the target value and detects the actual value, and the tightening is performed during the process. The tightening c-1 process can be monitored within predetermined limits by the reverse inference that results therefrom.

In the actual application of this method, the tightening forces determined from the cutting data and required to carry out the process are applied to the device in the form of limit values and stored. The inspection interval, ie the number of tightenings to be inspected, is also provided to the device and stored.

In order to carry out the method according to the invention, the device monitors the tightening, which is important for the transmission of cutting forces, by integrating the sum of the forces.
For the tightening device used, the number of tightening elements, for example the number of pawls of the pawl chuck used, must also be entered. This data input is performed only by an authorized person, such as an installer. This person switches the device from input operation to monitoring operation, thereby securing input data.

Now, the microprocessor of the device to be used gives an instruction for the initial tightening force during the process, detects the force for instant tightening, displays this r'L, and outputs this. Remember. In general, the microprocessor compares the momentarily existing tightening force with the limit value and sets the actual value, which is greater than the limit value, to start the machining process.

If the measured value is smaller than the setpoint value, the start of the machining process σ) is prevented either directly via the output signal of a device connected to the machine or indirectly by displaying a signal, such as lighting a lamp. Furthermore, the device can display the reason why the start of the process was prevented.

Upon transition to monitoring operation, the tightening process is counted and stored, and when a predetermined value is reached, measurement is performed again. − If the measured value is greater than the limit value, the machine tool is started again. Measured values are stored continuously according to a predetermined measurement cycle. Taking into account these stored measurements and test intervals, the device's microprocessor determines whether a specified number of tightenings is expected to be below the limit value within the next test interval, including the process. I can't make any predictions.

When this happens, the number of tightening steps that can still occur is indicated until a limit value is reached, or a new start of machining is prevented by a locking of the machine tool spindle.

The device implementing the method of the invention is capable of detecting the tightening process and/or the measuring process to ensure that the measured data processed actually correspond to the actual data of the tightening device. can. Manipulation is thereby largely avoided.

Based on this concept of a monitoring device for tightening equipment, which is the basis of the present invention, the tightening necessary for the cutting process is performed to prevent the force from unexpectedly dropping below a predetermined value. In this way, accidents and damage to machine tools can be prevented.

In the drawing the lines clarify the method according to the invention.

A diagram is shown.

This diagram shows the variation of the tightening force F with respect to time t, which is represented by the number of measurements or the number of tightening processes. There is a process of tightening a certain number of times between each measurement,
This number of times can be selected depending on the processing and the type of workpiece.

Initially, the tightening force remains almost unchanged with respect to the number of measurements, and then the tightening force gradually decreases. This reduction results from increased friction in the transmission of the clamping device that transmits the clamping force from the force generator to the clamping element. High surface loads occur in this transmission during force transmission. This force transmission surface should be lubricated with grease. Due to the large loads, the grease gradually increases friction due to the extrusion process, reducing the efficiency of the transmission. As a whole, this results in line diagram 7)
), the force of the tightening is reduced as the tightening is obtained by the device.

The tightening force is measured by a force measuring device.The tightening force is given to a microprocessor, which, after being given several measured values, determines the tendency of the tightening force change. find out This tendency is shown in the diagram with a dashed line.

From this tendency, it can be seen that in the embodiment shown in the drawings, the force at the ninth measurement diameter tightening is equal to or less than the limit value 'FG. As a result, the necessary retaining power no longer occurs. In other words, the workpiece will come off the clamping device.

By stopping the machine tool before the 10th measurement, and stopping the drive device based on an optical signal or an acoustic signal, by a worker or automatically by a signal to stop the drive device via the machine tool control device, Prevent the workpiece from coming off.

Thus, by direct measurement and the method described above, the previous weaknesses of machine tools, namely the lack of reliability of the process due to the clamping of the device and the lack of reliability in the process, can be eliminated. The tightening device can only be used if the clamping device is large enough to securely secure the workpiece in the case of

[Brief explanation of the drawing]

The figure is a diagram showing the tightening force of the tightening device over time.

Claims (1)

[Claims] 1. A method for monitoring the force of a machine tool tightening device by sequentially determining the force and comparing the measured value with a predetermined limit value. Tightening is performed sequentially within the machining process of one series of workpieces in a selectable periodic period. During the process, the instantaneous tightening of the device measures the force, and the tightening is determined from the measured value. Tightening with respect to the number of processes is characterized in that it detects the tendency of force change and generates a signal to interrupt the machining process before it is expected to be below the limit value after the last measurement process. Tightening the device is a force monitoring method. 2. Is the machining process restarted when the machine tool stops operating due to a signal? The method according to claim 1, characterized in that the method automatically prevents